Rot at able tremulant sound



Jan. 9, 1951 D. J. LESLIE Re. 23,323

ROTATABLE TREMULANT SOUND PRODUCER Original Filed July 9, 1945 '7 Sheets-Sheet 2 ATTORNEY J 1951 D. J. LESLIE Re. 23,323

ROTATABLE TREMULANT SOUND PRODUCER Original Filed July 9, 1945 '7 Sheets-Sheet 4 Tic. 15

NVENTOR Dona/0 J [es/f6 MWflW ATTORNEY Jan. 9, 1951 D. J. LESLIE 23,323

ROTATABLE TREMULANT SOUND PRODUCER Original Filed July 9, 1945 7 Sheets-Sheet 6 it}. BB

V 218 22c i 717 I MCKOP/Yd/Vf 1 42 Al'iPl/flE/P f d 50mm; (2 54mm 35 E3 226 I J \NVENTOR I ATTORN EY Jan. 9, 1951 J LESLIE Re. 23,323

ROTATABLE TREMULANT SOUND PROfiUCER Original Filed July 9, 1945 7 Sheets-Sheet 7 \NVENTOR Dona/d JT Zes/x ATTORNEY Reissued Jan. 9, 1951 PRODUCER Donald J. Leslie, Wilmar, Calif.

Original No. 2,489,653, dated November 29,1949, Serial No. 603,850, July 9, 1945.

Application for reissue March 13, 1950, Serial No. 149,230

' 13 Claims. (01; 181-27) Matter enclosed in heavy brackets appears in the original patent but forms no part this reissue specification; matter printed in italics indicates the additions made by reissue musical tones, as by electrical or electro-mechani:

cal means.

I This application is a continuation, in part, of an application now abandoned, filed on December 10, 1940, in the name of Dona d J. Leslie under Serial No. 369,413, and entitled Acoustic device.

In playing an ordinary musical instrument, as a stringed or windinstrument, or in singing, .the pleasing quality of the music may beenhanced, as is Well known, by producing a pitch tremolo or vibrato. This vibrato effect, in the case of an instrument, is'produced by a slight, rapid motion of the finger on the appropriate key or string, and which causes cyclic and rapid minor variations of pitch.

It is an object of this invention to impose pitch tremolo or vibrato, by mechanical means, on a musical tone.

It is another object of this invention to provide means for operating sound producers incorporating air actuators to secure vibrato effects in a simple and effective manner.

It has been found that cyclic motion at an appropriate rate of a channel forming means utilized for transmitting a tone suffices to impart vibrato to the tone. Thus, it is another object of this invention to obtain vibrato or tremolo effects bycyclic motion, such as may be pro-,-

duced by rotation of a sound transmitting;

channel.- v v a It is another object of this invention'toprovide a horn or other means forming a sound channel having special radiating properties, whereby the character of the vibrato is improved. p It is another object of this invention to pro videan arrangement whereby it is possible; to

alter the characterqofthe vibrato I v 'It is known to provide apparatus which,. byappropriate synthesis of electrical currents, producestones which have timbres the same as tones tag'es, and has other objects which may be made: more clearly apparent from a-consicleration ;of several embodiments of the invention. For thisf v purpose there are shown a few forms in the;

' drawings accompanying and forming part ofthfef present specification. These forms will now. be described in detail, illustrating the general prini cipEes of the invention; but it is to be understood that this detailed descriptionis not to be taken.

producedby any ordinary musical instrument.;

An electric organ, for example, is capable of pro ducing-tones having the characteristic'sound of organtones; although no organ pipes are utilized. lt is; another object of this invention to produce a pitch tremoloby mechanical means in such electrical apparatus.

When sound comes from a restricted locality, there are directional and other effects that are undesirable. It is still another object of this ipvention to avoid this-point source effect.

This invention possesses many' other' advan' T in a limiting sense, 'sin'ce'the scope of the inve'n tion; is best defined by the appended claims In the drawings:

' Figure 1 is a pictorial view of 'a cabinet for housingone form of the apparatus;

- Fig. 2 is a rear elevation of the cabinet-e; part of the cabinet being broken away; Fig. 3 is a section on an enlarged scale, as seen; onp1ane3 -3 of Fig. 2;

Fig. {i is a detail section of Fig. 2 Y 1 Figs. 5 and Gare fragmentary detail sections} as seen on correspondingly numbered planes oi Fig. 2; Fig.7 is a detailsection on anenlarg ed scale; as seen on plane l.. l of Fig-5; 1 f Fig. 8 is a detail section on an enlarged scale, as seen onplane 8 B of Fig. 6; p I Fig. Bis a section similar to Fig. i, but of ,a

as seen on plane modified form of the invention;

Fig. 10 is a transverse section, as seen on plane n w ..9;- Figs. 11 to 14 inclusive are diagrammatic show: ings of modified forms of the apparatus; 7 n; 15 is a;vie w similar to Fig. 2, showing a modified form of apparatus; v Q Fig; 16 is a vertical'section showing another modified form of apparatus; v Fig. l'if is a plan view of, the apparatus of F -l y :2 Fig. 18 is an elevation as-seen from the righthand side of Fig. 16; I Fig 19 is a view similar to Fig. 18, but show ing still another modified form of apparatus; Fig 20 is a diagrammatic showing of another modified form; of apparatus; Fig. 21 is an elevationiof a further modified tormof apparatus;

22 is an elevation as seen from the'lefthand. side of Fig. 21; I Fig. 23 is a diagrammatic showing of anotheii modification of the invention; i} MFigVZ tis a schematic showing of still another; form of apparatus; .25 is a fragmentary section on anenlarged scale, taken as indicated by line -25 on Fig. 24;

ing to the vibrato.

patterns useful in explaining certain aspects ofthe invention; and

Fig. 30 is a fragmentary view similar to Fig. 24,

showing a still further modification of the invention.

When a tone is to be produced "by electrical means employing apparatus including a loud speaker, the invention makes it possible to provide a tremolo effect in a simple manner; more specifically, by providing a sound transmitting channel for association with-the apparatus, and

causing the mouth of this channel to rotate. For

example, in one form of the invention, this mouth may serve to emit the sound from the speaker, the "rotation thereof being such as to cause the mouth to 'move alternately toward and away from the bearer at a frequency correspond- In another form of the invention, the sound transmitting channel may serve to transmit sounds from an appropriate source of tone to a microphone which, in turn, passes current impulses to the speaker. In this case, the rotation :of the sound channel is such as to cause the mouth, which receives the tone from the source, to move toward and away from' the source. In either case, the pitch of the sound heard by "the listener is alternately increased and decreased. 7

It has been determined experimentally that the vibrato not only imparts a pleasing gliding quality to the tone, but also determines the richness of the tone. For such a result, the speed of rotation should be between, about 300 and 450 revolutions 'per' minute, producing a tremolo of between five and seven cycles 'per second. At rates below these, the tone does not give singleness of pitch, the disturbances in the pitch be? ing perceived as occurring successively in the tones. Furthermore, th richness of the tone is re'duced- At rates above these, the richness gives way to an experience of increased compiexity, and the gliding character of the tone is lost. Accordingly, the rate of rotation of the sound channel'is confined between narrow limits."

In order to produce the proper vibrato effect, the speaker through which the sound passes may be moved cyclically between five and seven cycles per' second, as by rotating" the speaker. 7

A rotatable speaker has certain. drawbacks, such as the need of rotating a relatively heavy object and of providing a slip "r'ing connection to pass modulated current to the speaker. The same results may be obtained by providing a stationary speaker, or other sound generator, with a directional horn which is rotated about the speaker. Such anarrangement is shown, for example, in Fig. 2 of the drawings. On the other hand,- a rotatable speaker is easily connected with the directional horn; and there is no attenuation of high frequencies due to the need of employing a horn providing a bend, as iii' 'the case of a stationary speaker. Such a rotatable speaker is shown in Fig. 21.

Similar results are also obtainable by providing a revolving microphone which *feeds "into a conventional speaker." Since' a microphone so arranged moves alternately toward and away from the source of the sound which is being picked up, the pitch of the sound picked up and transmittedto the speaker, *oro'ther transducer such as a recording mechanism, will vary. Anar-' rahgement of this'kind' issh own diagrammatical- 4 ly in Fig. 23. However, to avoid the inherent difliculties of a rapid;.y moving microphone, such as vibration and the need of slip ring connections forthe microphone current, it, may be preferable to use a revolving directional horn which feeds the sound to a stationary microphone. Such an arrangement is shown diagrammatically in Fig.

Referring to Fig. 2 of the drawings, a high frequency speaker or sound generator i and a lower frequency speaker or sound generator 2 are shown as housed within a cabinet 3. Associated with each speaker respectively are means formtended for use in connection with an electronic ing directional horns 4 and 5 (see Figs. 5 and 6). Each of these horns forms a sound channel having a mouth or sound emitting opening spaced from the axis of rotation. The horns 4 and 5 arerotatably supported in the cabinet 3 and are arranged to be rotated bymotors 'l and '6 respec* tively. To allow the sound from the speakers to pass out of the cabinet freely, a number of openings are provided. Thus, near the bottom, each side, as well as the front and back of the cabinet has openings, such as 8, 9, and It (Figs. 3 and 6) which may be covered by louV-res or grills 12, or by a loose fabric as shown at [3. These.

openings are for the lower speaker 2. The entire top of cabinet 3 is open except for a covering Id of light fabric which permits free passage of sound from the upper speaker I.

As the horns 4 and 5 are rotated, the pitch of the sound reaching the listeners ear from the speakers varies and, as previously discussed, by appropriately choosing thespeed of rotation, a pleasing vibrato effect is obtained, as well as maximal richness of tone.

Also, since the sound is not'received by the car from a fixed and limited area, but, instead,

cabinet 3 is permanently closed on the front and sides 20,2I and 22, and is partly closed on the back by a removable panel 24. Cabinet 3 is also provided with an upper shelf 25 (Figs. '2, 5, and

7) for supporting the high frequency speaker I, together with its horn 4 and driving motor I, and a lower shelf 26 (Figs. 2, 6, and 8) for sup porting the low frequency speaker 2.

As before mentioned, the apparatus is indevice. Thus, the final amplifier stages of such a device may be conveniently placed on the'upper shelf 25, as indicated by 21- (Fig. 2 and con-- nected by means of a suitable cable 28 with indicated by 29 (Fig. 2) being -interposed in the connections to limit the frequencies supplied tothe respective speakers. The connections between: an appropriate amplifier and high and 'low' fre-f quency speakers are well understood by those skilled in the art and, accordingly, will not be d-;

tailed here. Appropriate leads (not shown) also supply current to motors 6 and "7, switches 'l5 and i6 (Fig.2), located on'thefe'xterior and near the top of cabinet 3, serving to control the 1110- tors respectively.

As clearly shown iri'Figs." and theh'ighfre quency speaker I is secured to the underside of a rectangular plate 30, as by screws 3|. Plate 30 may be of suitable relatively light material which machines readily, such as fibre, and is supported with respect to shelf by a box-like frame 32. Plate is provided with a central bore 33 which is aligned with the speaker opening 34. Bore 33 is provided with a counterbore 35 which has an anti-friction radial and thrust bearing 36 mounted therein. A long set screw 31, threaded into the fibre plate 30, engages the outer race 38 of bearing 36 and secures bearing 36 in plate 30. A pulley 39 with a fiat upper face 40 has "a tubular hub 4| whichis secured to the inner race 42 of bearing 36,-as by aheadless setscrew43.- t I Mounted on the upper facelllof pulley 39 is a horn 4, which horn extends upwardly-and away from the opening 41 in hub -4 l Horn 4 is preferably an exponential type horn, andserves to direct the sound waves'from speaker, these waves passing out of cabinet 3 through the open top thereof. To maintain the horn 4 in mechanical balance, a similar horn 48 may be mounted diametrically opposite horn 4. The sound waves, however, do not enter horn 48, a wall 45 serving to separate horn 48 from horn 4. f It is important that vibrations from the rotating apparatus be prevented from reaching" the cabinet. Accordingly, plate 30 is resiliently supported on frame 32; and frame 32 is, in turn, resilientlysupported on shelf 25 by means of rubber bushings 50. These bushings 50 each have a cylindrical body portion 5| surmounted by a flange 52, and are mounted in pairs by being inserted in a suitably sized opening 53 in the member to be supported, the flanges 52 engaging the opposite faces of the member. A screw, as 54, is then passed through a central opening in the bushings 50 into the supporting member, as 25, a suitable washer 55 being interposed between the head of screw 54 and the flange 52 of the top bushing 50. In this manner, the lower flange 52 is interposed between the member 30 or 32 and its support, the bushings also preventing the screw 54 from directly contacting the supported member. Thus, transfer of vibrations between the horn and its support is effectually prevented. T The motor I rotates the horn 4 by means of a belt 51 engaging pulley 39. The motor 1 may be adjustably supported on a bracket 58 .in

cabinet 3, suitable means such as resilient pads 59 being provided between the bracket and the cabinet to prevent vibration from the motor I reaching the cabinet. The low frequency speaker 2 is also provided with a revolving directional horn 5 (Figs. 2, 3', 4, and 6) which, however, is shown. as not being of the exponential type. Horn. 5- is built of upper and lower discs 6| and 62, joined'by vertical walls 63. The top disc6l is provided with openings '64 to admit the sound from the speaker 2, the sound passing outwardly through opening 65 inwall 63. The lower disc 62 is imperforate. The horn 5 is mounted on a central, vertical shaft 66 which is rotatably supported by antifriction bearings 61 and 68 at its upper and lower ends respectively. Bearings 61 and '68 are respectively supported in fibre blocks 69 and 10. Block 69 is supported on a bar II spanning an opening 12 (Fig. 8) in the shelf 26, which opening serves to pass the sound waves from speaker 2 into horn 5., To prevent undesirable transfer of vibrations between horn 5 and the cabinet 3, the block 63 is supported on bar Ilby means of rubber bushings I5 and screws 16in a manner 1 bar 'I'l (Fig. 9) 1 extending diagonally across the bottom of cabinet 3. A pulley-131s mounted on the outside of disc 62,2. beltpassing over the pulley and operatively connecting the horn 5 with motor 6 (Fig;

3). The motor 6 is adjustably mounted in cabinet 6 by brackets 8i, resilient pads 32 being interposed between brackets 8| and the wall 2| which supports them to prevent any vibration from the motor 6 reaching the wall or the cabie net. It is to be understood that the horn structure 51,62, 63, etc. is rotatively balanced with respect to shaft 66. To reduce the resistance imposedon its rotation by the surrounding'air, the peripheries of discs 6| and 62 may be joined by a piece of light fabric I31. This, in effect, makes the structure cylindrical and eliminates fanning of the air as the structure is rotated. Y

To improve the quality of the low frequency production, it may be desirable to use the reflex principle. The low frequency speaker 2 is shown as of the type having an air actuating cone of large diameter, for example, fifteen inches. Speaker 2 is supported above horn fifwith cone '85 directed downwardly and axially aligned with the horn by means of a table 86 (Fig. 6) Table 86 comprises a board or plate 81, which may be square for, convenience of fabrication, spaced above shelf 25 a short distance by means of blocks 88 at the corners of plate 81. Plate Bl supports the speaker 2 by having frame 89 of the speaker secured to. the plate. This plate 6'! is provided with a central aperture of a diameter somewhat less than that of cone 85,,and a tube 9| extends from aperture 93 down through opening 12 in shelf 25 to disc 6|, terminating abovethe disc Bl to provide suitable running clearance. Thus, sound waves-from the lower, or inside, surface of cone 85 pass into horn 5 withoutmingling with the sound waves from the upper 01 'outside surface of the cone 85. These latter sound waves pass downwardly in the space beg tween plate 81 and the sides of cabinet 3, and enter horn 5 through the annular space 92 defined about tube 9| by the opening 12. 1

While the speakers have been shown and described as mounted in a single cabinet, this is merely a convenient Way of assembling the apparatus, and makes a compactand readily portable unit. Thespeakers could be in individual cabinets and spaced apart if desired. Further, additional speakers may be provided for either frequency if desired. 4 Further, it is not'necessary that the horns from the high and low frequency speakers rotate in synchronism; in fact, best results arefrequently obtained by rotating the speakers at different speeds and in opposite directions.

As an alternative to providing the fabric I31 directly on the structure 5 to reduce the wind resistance, a well I60 may be formed in which the structure 5 revolves, as shown in Figs. 9 and 10. This similarly preventsffanning of the air by the rotating structure. The horn 5 is supported between bar ii on shelf 26 and diagonal bar Tl, all as before. A ring llil, formed of a light metal angle and having a diameter slightly greater than that of the horn structure, is mounted on the under side of shelf 26. A similar ring I 02 is mounted entire. unnerside of bar-11.; Fabriefiifl; encircling. thehom structure 5 is secured.

tween the. angles. The effect. secured by the rotation of the: horns; as heretofore stated, is most. satisfactory when the speed of rotation is about 400. revolutions .per' minute, and which fixes the cyclic variation of pitch at the rate of about seven cycles per sec-- 0nd. The actual variation in pitch is aiunction of the instantaneous relative linear velocity of the; source with respect to the ear; and. thisdepends, in part, upon the radius of the eccentricity of the mouth. or sound emitting opening of. the horn to the axis of rotation. This distance is represented, for example, by the radius of the drum 45 of 5,. and may. be chosen to suit the. particular appli cations; for example, the radius may be as little three: inches or as much as a foot or two. Thatthe rate of seven cycles per second. is an optimum. is. shown. in the. work Hearing jby- Stevens and Davis, published by John Wiley and Sons, at pages 234 to 241. Apparently, this seven cycle value must be closely approached to obtain;

the most pleasing effects.

- As previously mentioned, a tremulant effect is-similarly obtainable. by providing a stationary microphone with a. rotating directional sound channel forming means feeding sound to it- Thus, in-Fig. 11, a microphone of any preferred type is indicated by I I0 and is. shown as provided, with a directional horn IH, rotatably supported by an anti-friction bearing H2. A motor [[3 rotates horn. l I l. at the desired speed by means of a belt H4; The sound emanates from a source ([5 a suitable sound-proof enclosure [18, indicated by broken lines, being provided to enclose the source and the microphone. The impulses from the microphone are amplig I fi'ed by a suitable amplifier HS and are then fed to a speaker H7, which may be a conventional speaker or speakers, or may be a. conventional recording apparatus.

{It is also possible to combine the rotating speaker arrangement with the rotating micro phone. Such an arrangement is indicated in Fig. 12, wherein a speaker "I28, havinga 'dirc' tional horn l2! rotated as by a motor 22, is substituted for the translating device ll-l of- P Itis sometimes desirable to vary the apparent the entire sound produced-will have tremolo; and

by providing rnearrswhereby the amount of thisportion'relative to the total sound may be'altered: at will. Ihcre are several ways in which this can be done; in 13,'a'rotating directional i'25,rdriven by a motor I26, is used to dis tribute the sound from a stationary speaker [21. A'sco'nd speaker l28fis provided with a station- :i'ry'horn I29; andfspeakers I21 and [28 are conhectedto a common amplifier I30 by a dividing network 131' including a potentiometer I32.

By adjusting the position 'of arm I33 of the potentiometer I32, the resistance value in circuit with each speaker may be altered, with resultant changes in the "amount of sound delivered by each speaker. It-is to be understood that either the high frequency speaker and horn, or the 'low' frequency speaker and horn of Figs. 2 and 3 may be replaced by a-cor'nbination such as disclosed in Fig. 13,- or that the high" and low frequency speakers may each be replaced by such an arrang'ement, adapted to reproduce highahd low frequencies respectively. It is also tobe under Aa'seeond low frequency. speaker may. also stood that speaker is may equalw ell-be oi someone-net IhFig. 15,, a cabinet 3 is shown wh'ch houses irequemy'speaker I: and. a low irequency speaker 2,,provided respectively with rotating;

direc-tional horns- 4 and. 5. These speakers erectedinet, and is arranged to be fed from. a dividing.

network: ilk similar to that shown at [St of EigI lfitandinterposed-in the leads. to speaker In.

provided and. is indicated. at. ITB. This may e of the. moving conetype wherein no horn isiiti lized. the sound-being emitted through. asuitab openin in the sideoi cabinet 3. This. spe flat-is fed irom an appropriate dividing c' 1130 interposed in" the leads to speaker 2..

is possible. to use a single speaker and vide the sound therefrom so that summer. t has a. tremula-nt. efiect while the remainder does not. Thus,,--in li' ig. ii; a. stationary speaker 1.35 deliverssound to a. rotating directional horn L31 Suitable means are. provided for varyi'n he distance of the mouth I311 of horn 131' f roni thiji speaker I36, thus. providing a. variable opening. permitting some of the sound waves topass from the. speaker without passing through the revolv-f ing horn 131.. One way in which such a variable opening can be. provided will now be described. i lorniiift rotatably supported by means of a radial and. thrust bearing [39 on a movable platform Ill}. which .also'car'ries motor ['41 for driving the horn; Platform I 41! is guided for vertical movement with respect to the speaker [36 by suitable'guide bars [43 on a base plate [432, and isadjustably ported with respect to the. base plate l42- by'a threaded rod 4 engaging nut I45 fixed on plate {arm 0. Rod-I44 is rotatably supported in'fi'xd axialposition with respect to base I42 by a suit;-' able bearingfllfi and ism-ranged to be rotated by a hand crank 1'41 through intervening gearing 1 M8. Obviously, if horn I3! is positioned-immedi;

ately adjacent horn I35, practically all sound from the speaker will have tremolo. By moving the horn i f3] *kiownWaidTy' o that its"mouth' I38 is spaced"from "the'speaker,' some of the sound from the speaker will pass directly to'th'ehearer without passing "through the horn; hence will have no tremolo} j The'res tof the sound pass through the horn and have tremolo; By varying the spacing between the mouth I38" horn -I3Tand speaker #36; the strength of the tremolo can be varied. In several iorms of the invention so' far de scribed, the vibrato'is obtained by cyclically mov ing an opening through which the sounds are emitted toward and away from the 'listc'nefi' as byrotatin at-directing sound horn which provides such opening' With a rotating horn, the

rate of'm'ovement ofthe mouth toward and away from the listener is a function of the answer position .of'the hornpas well as of the length'ef the 11mm; suchrate" of movementapproaching zero as the approaches "a position pointing at list ner. "Th-11S, the frequency change and the vibrato-also approach serial" that, the amplitude of the sound is at a maximum;

with respect to the listener with the horn pointing at him, which further reduces the vibrato effect.

By modifying the usual radiation pattern of a sound horn to obtain broader distribution of the sound, more of the sound from the horn will be heard when the horn is moving toward and away from the listener Also, the amplitude of the sound will be decreased when the horn is pointed directly at the listener. In this way, a smoother and fuller vibrato effect is obtained. This is particularly important at the higher frequencies where the usual sound horn is highly directive. Furthermore, it may be desirable to provide that all of the sound moves, as nearly as possible, at the same speed with respect to the listener at any given moment. For this purpose, the horn mouth, or-other sound emitting open ing, should be narrow or of small angular extent in the plane of its rotation.

A speaker adapted for operation in the lower frequencies requires a mouth opening of considerable area; the mouth shape is thus preferably such that its dimension parallel with the axis of rotation is substantially greater than its dimension in the plane of its rotation. A horn of this nature is illustrated in Figs. 16, 1'7, and 18.

It can be shown that such a horn, having an openingwith a dimension in one direction equal to several wave lengths of the sound emitted, and with'a dimension in the other direction of less than one-quarter of such a wave length, is highly directive in the plane of its length, or long dimension; but has a broad radiation pattern in the plane of its width, or short dimension. Thus, a horn with a mouth of this character has the double advantage of providing a broad radiation pattern, as well as causing all of the emitted sound to advance with respect to the listener at a more nearly constant instantaneous speed.

In Figs. 16, 1'7, and 18, a speaker I 8| is shown which may be of the type employing a moving cone as the air actuator. The speaker is supported within a casing I82, and with its axis vertically disposed, by being secured to th top wall I83 of the casing I82. The casing or enclosure serves to prevent radiation from theback of the speaker cone, and may be filled with rock wool or other sound absorbent material. An opening I83a in the top wall I83 serves to transmit sound waves from the speaker IBI to a horn I84 mounted on the casing I82 for rotation about the speaker axis I85. As clearly shown in Figs. 17 and 18,. the mouth lB4 -a of the horn I84 is quite narrow in the plane of rotation of the horn to ensure that sound waves emitted by the mouth all move at substantially the same speed with respect to a listener, as well as produce a brrad radiation pattern. At the'same time, the mouth I84a is quite long in a direction parallel with the axis to provide the necessary area.

The horn I84 is supported and guided for rotary movement by means of a stationary vertical shaft I88 mounted in a bar I81 extending across the opening I83-a and fixed to the top casing wall I83. This shaft I88 extends through the "upper wall of the horn I84 into a thrust'bear ing structure I88, a hardened ball I88 therein supporting the weight of the horn by engagement with the end of the shaft I36. A radial bearing I88, supported in the throat'of the horn by. a bar ISI extending across the throat of the horn and engaging the rod I85, serves to ide the born for rotary movement about the rod I86.

1! counterweight I82 adjustably mounted man 7 1 The horn I84 is arranged to be rotatedat an appropriate speed, as previously discussed, by a small electric motor I94 mounted on the casing I82," and connected by a belt I95 to a pulley structure I98 secured about the throat of thehorn. A ring I 91 is provided about the opening I93 a and telescopes into the throat I'84b of the horn I84 for sealing against escape of sound passing from the speaker I8I to the horn.

The character of the vibrato may be varied by providing rotating horns, such as just described, with differently proportioned mouths; 'for ex ample, with mouths variously inclined in the motion of rotation; Fig. '19 is a front view simi 'lar to Fig. 18; and shows a horn 2'00 which'hasi-a -mouth 28II-a, the long dimension of whichis oblique with respect'to a plane normal to the axis of rotation. This angle of obliquity may be chosen as desired, as indicated by the mouth out- "A rotating horn, such as any 'of the types so far discussed, may be employed as shown sche matically in Fig. 20 to impart vibrato to a steady tone as from a source 20I. This tone afiects'a fixed. "microphone 282 'to supply modulated current to an amplifier 283 operating a speaker 204.

.The'sound from the speaker 204 is fed to a' directional'horn 205, supported for rotation about a vertical axis by a bearing 286 and appropriately driven'by a motor 201. cated'by broken lines, is provided for confining the sound from the source 20L.

In all of the arrangements'so far discussed, a

rotating horn has been provided in connection with a stationary speaker or microphone." It "may be desirable to provide for rotating the "speaker or microphone, as in this way a better connection to the horn or other means forming the rotatingmouth is possible, and the necessity of employing a curved horn is obviated.

Figs. 21 and 22 show a rotating" speaker.

.Therein; a speaker 2I0 of any suitable type is --shown as enclosed in a casing 2 which may be ing structure 2 I 8.

filled with-sound absorbent material'to' prevent sound radiation from the back of the speaker. :A directional horn H2 is mounted on the front of the casing 2H for cooperation with the speaker 2IIl, a suitable counterbalance 2I3 being provided on the back of the casing. As shown in Fig. 22, the mouth 2I2-a of the horn 2I2 'is of small angular extent in the plane of rotation andof considerable length parallel with the axis of rotation, thus providing the advantages of a narrow source and a broad radiation pattern, as previously discussed.

The speaker 2H! and the horn 2I2 are supported for rotation about a vertical axis 2I4 as by the casing 2II being secured to a vertical.

shaft 2 I 5 rotatably' supported by a suitable bear- The casing 2| I is shown as arranged tobe driven by a small electric motor '2II connected by means of a belt 2I8 with'a pulley/"2H! secured to the casing. Modulated current isfed to the speaker 2I8 by means of slip rings 22'9"and 22I. The horn 2l2, being withoutbends, does not materially" attenuate the higher frequencies.

In the form shown An enclosure 208, indi I in Fig. 23, a rotating micr'opho'ne 2234s provided. for. receivingitone 1! 1mm a sou-roe 2-24. memo-hone .223 is su {ported for rotation about a vertical axis by a. structure 2'25, and is' arranged to be driven at an 'apm'opriate speed by means of a afiotor 22 6. Current from the microphone 223 is 5 fed by means 01' a slip ring connection 221 to an amplifier 228 wh ch anti-rates a speaker 229. It is not necessary that this sneaker have a rotatsag channel or sound emitting opening, since the desired vibrato imposed by the rotation of the microphone 223.

For frequencies where a. large opening is required, the horn justdescri bed may be preferred. Iifowever, horns of rather small dimensions are commonly employed for medium and high ire- Such aho'rn can be readily fitted with type of deflector at its mouth ,for altering the radiation pattern of the horn'and obtaining vibrato: An arrangement of this sort is shown in 24 and "25... In"Fig. 24 a direcdeional sound horn 135, adapted to transmit sound from'a source 236, is arranged to be rotated at =5, suitable speed about axis 231,- spaced from the mouth of the horn, as by a motor 238.

such a horn will have a radiation pattern or the form indicated by the broken lines Fig.

The ssound emitted will have vaxpeak zam-nlidirectly in front of the horn, the higher imqucncies having strongly r'lirect'ional charactenet-ice as "indicated by curve .marked A, and

the'medium freonencies be'ing more widely dis- I as indicated by the curve din-providing a deflector comprising a pair of plates 23! and 2411, oonositely inclined across the mother the horn 12.35 in the plane of rotation :of thelnorn, the radiation pattern may he changed have a form such as that indicated by the wave C in Fig. 28,. Th rein. it wi'llhe noted that the peak amplitude in flout of the horn has been wbstantially reduced and the.-.scund distributed :overn wider area. Fnrthermordthe directional gnomes of the higher frequencies have been decreased so that these and the medium fremanholes about the samedistribution. :Such a deflector also afiects the vibrato y increas ng thev a arent .sleneth so! "the horn which increases flae flopplerofiect. e 1

- Asishown, the plates .2 3'9 sand-240 are large with to the mouth of the horn 2 .35, and are disposed at right angles 'vvith'respect to each other. radiation patterns may be provided by larger or smallerplates for a .difierent inclination, or both. Thus, in Fig.v 26, several 96h; ofsmaller nlates 24.1 and 242 more steeply :inclind are shown as provided across the mouth or the horn 235. Therad-iation pattern'for a horn yith a-defle'ctor will he of the type indicated in 2-9, and is generally intermediate the curve's'A and B of Fig. 27 and-the curve C- of Fig. :38. The amplitude peak directly in -:front of the -horn is not very pronounced :and the sound is qui.te--broadly distributed, the medium frequencies (curve 'D.) being somewhat more widely disbributed than the higher Irequencies (curve E).

. The directional characteristicsof a horn in the rlane of rotationstrongly aii'fect the vibrato, the same. characteristics in a plane normal stherieto have no effect. iAccordin'gly, if a. horn arranged so that its ,directivity is efiective in fithcrits plane :of rotation or at 90 thereto, comidifferent efiects can be obtained. Other effects can also be obtained. jnositioning :the

directed in an intermediate -=position.

.11m such. adinstment r the-mouth, the

ithilifflerentdirectional-slicers in the two planes of sound in said other channel.

"horn 235 is formed of two sections :tii -aand 235-4), rotatably coupled by :a collar iii-n. Thus, the outer end section 235-a, which has different directional properties in 'di fierent-planes by virtue of the deflector plates 23,9 and 148,- or 26] and 242, maybe adjusted to vary the vibrato. :set screw 24,3 serves to secure the horn section '2-35-a in adjusted position.

It may be desirable to provide a deflector which will produce the same radiation pattern all planes. For this purpose, a horn .such :as 2.35 may have a conical deflector 2'45 .suitablyssuppor-ted at its mouth, as shown in Fig. .30.. Obviously, the proportions of the cone may ,be varied to produce different characters of vibrato. v r

.The aspects of the invention illustrated in Figs. 1Y6 to :19, inclusive, .21, 22 and 24 to .30, inclusive, form the subjects matter of divisional applica- 'tions Serial No. 90,649, .filed April v30, i949, ior Acoustic apparatus, and Serial No. 90,650, ,filed April .30., 18.49, .ior Sound .distri-huting -appara- $115. 2 'fI he inventor claims: 7 1. In an apparatus of the character descriioed, in combination, a .low frequency speaker, having a cone adapted to deliver sound waves from its inner as well as its outer surface, an enclosure for the speaker, one wall of the enclosure having-an only through said opening, said support also pro.-

viding a passage for the sound waves from the hack of the cone to the same opening, a dime,- :tional horn tor receiving the sound waves .iroin one of said passages, and means for rotatingsaid horn. 2. In-an apparatus {of the character. described, in combination, a low frequency speaker, l1aving .a. cone adapted to -.deliv-.er sound Waves from its inner as Well as its outer surface, an enclosure for speaker. one wall of the enclosure having an opening .to pass the sound waves .irom the speaker, means tosupport the speaker. adjacent the opening, sup lant including means defining a Passage for sound W3,YS from the front of thecone only through said opening, said support also projviding a passage for the sound waves from this backof the cone .to the opening, .a directional horn .for receiving the sound waves from said opening, .a rotatable support for the horn, and means 'rotatethe horn.

3.111 apparatus for adding pitch tremolo to musical sounds [devoid of pitch tremolo], a cabinet, stationary high and low frequency speakers in the cabinet, supported respectively adjacent the upper and lower ends thereof, a directional for each speaker rotatablynsupported in the cabinet, and means :to rotate .the .horns, the-re being openings in the cabinet to permit egress of sound.

4.111 apparatus for adding a tremulant efiect to musical sounds [devoid of pitch tremolo], astationary sound translating device, a rotating directional horn having a sound channel opera= tively associated with said device andex-tendi-ng transversely of theaxis thereof, means forming another-sound channel operatively associated with said device, and means to control the passage .5. In apparatus :for adding pitch tremolo 10 .musical sounds [devoid of pitch tremolo], :st a; n rvx o nd atin e a sm fprininearot tins; irec qn l'sqlm 1. .e ii

said mechanism, means providing another sound channel for said mechanism, and means to alter the volume of sound in one channel compared to that in the other channel.

6. In apparatus for adding pitch tremolo to musical sounds [devoid of pitch tremolo], sound translating mechanism, means forming a rotating directonal sound channel having a throat for cooperating with said mechanism, and means to adjust the spacing between said throat and said mechanism whereby the transfer of sound between said sound channel and the translating mechanism may be varied.

7. In apparatus of the character described, a sound translating device, means forming a pair of channels for simultaneous cooperation with said device, means for imparting relative motion between one sound channel and the device for produclng a tremulant effect, and means for adjustably distributing the sound between the two channels.

8. In combination, means forming a common source of energy for producing sound waves, means providing separate sound channels cooperating simultaneously with said common source, means whereby one of said channels may be moved cyclically for producing a tremulant effect, and means for adjustably distributing the relative amounts of energy between said channels.

9. In apparatus for adding pitch tremolo effects to musical sounds, a pair of stationary sound translating devices having different frequency ranges, a common source of electrical impulses for both said devices, a pair of means defining air columns, respectively associated with each device, each air column having an opening for emitting sound, and means for rotating both of said air column defining means in such manner as to cause an orbital motion of said openings.

10. In apparatus for adding pitch tremolo effects to musical sounds, a pair of stationary sound translating devices having different frequency ranges, a common source of electrical impulses for both said devices, a pair of means defining air columns, respectively associated with each device, each air column having an opening for emitting sound, and independently controllable means for independently rotating each of said air column defining means in such manner as to cause an orbital motion of said openings.

11. In a tone producing apparatus for an electrical musical instrument, the combination of a pair of loud speakers connected to receive the output of the instrument, one of said speakers being particularly designed to produce tones of a higher audible frequency range, while the other speaker is designed to produce predominantly the tones of the lower audible frequency range, a rotatable elbow-like deflector positioned to receive the acoustic output of said higher frequency speaker, and means to rotate said deflector at a speed inthe order of seven revolutions per second.

12. In a tone producing apparatus, the combination of pair of translators for converting electrical impulses into sound, one of said translators being'designed to produce predominantly tones of the'higher audible frequency range, the other translator being designed to produce predominantly'the tones of the lower audible frequency range; a common source of electrical impulses connected to both of said translators, means forming'a rotatable air column channel positioned to receive the acoustic output of said high frequency translator, said channel forming means having a sound emitting opening, and means to rotate said channel forming means to cause the sound emitting opening to describe a circular path at a speed of the order of seven revolutions per second.

13. In a device of the character described, a stationary speaker, a directional horn associated with the speaker, means forming an enclosure for the speaker and the horn, a rotatable support for the horn, and means to revolve the horn, there being peripheral openings about the enclosure substantially aligned with the opening of the horn.

DONALD J. LESLIE.

REFERENCES CITED The following references are of record in the file of this patent or the original patent:

UNITED STATES PATENTS OTHER REFERENCES Bartholomew, Acoustics of Music," 1942. Published by Prentice-Hall, Inc., Fifth Avenue, New York, New York- (pages 22 to 26). 

